Are these the right questions?
Well, I waited a few days to see what other major explanations people might have for the early March/May 2007 drop in new editors. So, again, I feel strongly that the drop was mainly due to the notorious banning of Wikipedia in U.S. schools and colleges, as demanded by academic officials beginning in February 2007. See the enWP essay about bans, with 19 news articles:
Other bans were suggested in England. Those early bans, coupled with the typical 3-month school vacations (June-August) seem to be what thwarted the English Wikipedia. Note how some similar reductions occurred in the German Wikipedia in early 2007 (which had the similar 50% of users younger than 22 years) despite deWP's faster initial growth of gaining new users, while the French Wikipedia graph shows only a steady, seasonal variation in adding new users, with no sign of bans in France, to deter new users from joining French WP. Because the French WP shows no signs (yet) of a dramatic decline in new users, the French statistics can be used as a control group, to exclude the effect of updates for MediaWiki release 1.09, as not having a strong impact to deter new users. Obviously any large colleges banning Wikipedia use, among 2,000 to 50,000 students per college, would cause a massive decline in user access during 2007-2008 and beyond. -Wikid77 19:37, 17 March 2011 (UTC)